Thursday Murder Club, The (Thursday Murder Club #1) by Richard Osman; 2020. Softcover.

Four septuagenarians with a few tricks up their sleeves
A female cop with her first big case
A brutal murder
Welcome to…
The Thursday Murder Club

In a peaceful retirement village, four unlikely friends meet weekly in the Jigsaw Room to discuss unsolved crimes; together they call themselves The Thursday Murder Club. Elizabeth, Joyce, Ibrahim and Ron might be pushing eighty but they still have a few tricks up their sleeves.

When a local developer is found dead with a mysterious photograph left next to the body, the Thursday Murder Club suddenly find themselves in the middle of their first live case. As the bodies begin to pile up, can our unorthodox but brilliant gang catch the killer, before it’s too late?